Heater for rods and tubes



HEATER FOR RODS AND TUBES Filed March 15, 1930 16' U'JUUUU 33(1):.

4&4 a x! :WQ F

Patented Mar. 7, 1933 UNITED STATES PATENT OFFICE EDWIN II'I'CE- NOBTHBUP, PBUGE'LOI, mm mm, ABSI IIGNOB '10 AJAX mm TBOTBEBIIC (XBPOB-LTION, 01' MAI PARK, mx'ron, NEW M, A (337F031- mm ron none mm mm Application ma 1mm 15, mo. Serial 10.486).

My invention relates to the inductive heating of solid and tubular articles both fixed and movable and to apparatus by which these methods may be practiced. The subject mat- 5 ter-herein is a continuation in art of my coand tubes.

Application 76,878 is in turn a continuation in part of the subject matter of myapplication, Serial No. 425,439, filed November 20, 1920, resulting in Patent N0. 1,566,500, issued December 22, 1925, and with which said application 76,878 was copending. The subject matter of Figures 17 and 18 o the atent has been continued throu h application 76,878 and affords basis-sub ect to the lines of division required by the United States Patent Oflice-for claims of the present application. 20 One of the purposes 0 my invention is to surround solid or tubular articles with a conductor through which high frequency current produced by a discharge gap is to be passed, and to heat them by the current induced pref- 26 erabl while they are passing through the coils ut permissibly during stops in step-byste feeding.

further purpose is to apply induction to a moving r0 or tube by a coil or coils sur- 30 rounding the rod or tube and through which current from a discharge gap is passed having a frequency above normalfrequen'cies and a corrected power factor.

A further purpose is to provide parallel coils'or turns rallied from the same discharge gapand all operating successively upon the same tube or rod fed through them for the purpose of adding successively increments of 40 heat to the rod, strip or tube passing through them.

A further purpose is to use a relatively low finding application, Serial umber 76,878,-

ed Decem r 21, 1925 for heater for rods to supply hlihel frequency induction also gap to supply higher A further urpose is to supply power-factor corrected current from a generator of multi-polar rotary type to an inductor through which a charge is to be passed to a transformer primary, to utilize current from the secondary of this transformer raised in frequency by condensers and a discharge gap surrounding t e charge.

A furtherpurpose where the voltage of the generator is suflicient to cause discharge across the gap is to su ply an inductor surrounding the char e om a rotary multipolar generator wit condenser power factor correction and through another circuit containing inductance, ca acity and a discharge equency induction for the same charge. 1

Furtherpurposes will appear in the speci fication and in the claims.

I have preferred to illustrate a few forms anly among many in which m invention may appear, selecting forms whic best illustrate the principles of my invention.

Figure 1 is a longitudinalsection of one form of inductor applied to a travelling bar or rod.

Figures 2, 3 and 4 are diagrammatic views showing different. circuit connections. V

In the drawing similar numerals indicate like parts. I

' Though I prefer to operate at a higher frequency than that of existing current supplies and gain considerable advantage from this, features of my invention are of advantage. whatever the frequency and are claimed accordingly.

In Figures 1 to4-I have shown diflere'nt ways in which current at more thamiormal frequency can be supplied to an inductor comprising a single coil or spaced coils opfrequency. for inductive heating of rods, ,erating upon the same moving'bar, rod, strip strips or tubes of magnetic material up to to nearly the point at. which they lose this property, to heat them beyond this point by a higher frequency from a discharge gap using the same inductor or part of the same inductor for both, either at the same time or sepa- 50 rate times.

or tube of regular or irregular shapeyor to aconducting content, to raise it to the'req quired temperature as for rivet heating, tube. or strip annealing or for other operations. By these diflerent illustrations I have intended'to indicate that the use of abnormal frequency this duty involves invention loo in addition to whatever merit may lie in the manner of applying it.

In Figure 1 I have shown a method of integrating the heating effects of successive coils through which high frequency current is passed in the heating of a bar or rod which is advanced to progress either continuously or intermittently as preferred, as by a set of rollers 20 and 21'suitably mounted and driven. The coils 22, 23, 24, 25 and 26 are here shown as helical coils nearly fitting the bar, wire, rod or strip 27 which moves in the direction of the arrow. I have not considered it necessary to illustrate the protecting covers for preventing undue cooling of the bar etc., between the coils, as these could exist in great variety. The coils could be water-cooled if desired as in the case of the annular coils shown in my patents. 1

The coils are shown as separate and as separately supplied. with high frequency current through transformers '28 whose primaries 29 receive current at existing frequencies. 'The secondaries are connected to the coils through condensers 30 which when charged discharge across gaps 31. They can be one long coil or a series of coils depending upon the rate of speed of the charge.

It will be evident that the methods and mechanism herewith are capable of use generally or to heat treat electrically conducting objects in motion or which are moved stepby-step between treatments, whether they be magnetizable or not; and that the treatment may be applied to the special form of objects to be treated by accommodation of the coils in shape to these forms. The materials primarily to be treated when not electrically conducting may be treated by mounting them on or incasing them within elec trically conducting objects in which the heat is developed. Mums heating is claimed byme in a separate application.

Where the tern erature intended to be reached is below t e point at which iron or steel loses its magnetic properties a much lower frequency will suliice than is required where the final temperature intended is above this point, with the result that a choice is offered for these higher temperatures between raising the frequency of the entire equipment to a frequency which will be effective above the decalescence point or raising the temperature in a part of the range required by an inductor operating at one frequency and utilizing anot er higher frequency through the same or a separate inductor coil or coils to attain the higher temperatures.

- It is very desirable that the frequency shall be high enough so that theener y induced shall notpass appreciably beyon the center of asolid bar or rod operated upon nor tend to pass appreciably beyond the inner wall of a tube which is being heated, and, as later pointed out, the size of stock operated upon therefore materially affects the choice of frequency.

It is my intention to include within 111 generator supply such generators and S110 use of frequency changers as may best suit the needs of the individual installation.

In Figure 2 I have shown direct alternator feed with power factor correction at 32 for the inductor coil 22' shown, fed'through a transformer 28 whose secondary is connected to a circuit generally similar to any of those shown in Figure 1, containing the condensers 30 and gap 31 for applying-high freguency to the coil. In this same coil also ows low frequency from the transformer 33 whose power factor is corrected at 34. The

high frequency is then superimposed on the low frequency in the same coil. Either the hi h or low'frequency can be used separately. n Figure 3 the lower frequency is passed through the coils 22 23 and 24 from the current source 35-, having its power factor corrected at 36. The last coil 24 also carries higher frequency supplied from the transformer 28 by the use of a gap 31 and condensers 30, generally similar to any of the be used where the voltage of the su pl line I is not high enough to operate the iso arge' gap.

Where the voltage of the generator 35' is high enough to operate the discharge gap 31, the arrangement shown in Figure 4 is permissible. Here part of the inductor 22 is supplied directly from the generator, with power factor correction, and a further part 23 of the inductor is fed through condensers.

Instead of directly heating the stock, I may heat an electrically conducting muflie andpass the stock through the mufie. I

In all of the forms where a plurality of turns per coil is used, I prefer to use a single layer coil of edgewound flattened copper tubing and find water cooling of the tubing very desirable.

In operation upon stock of the character treated herein, whether it be solid or hollow, of uniform or of irregular cross-section, the coupling increases with increased diameter of the stock as the gap required isapproxi- V to have efi'ective induction extend beyond the center of the stock. This would apply 5 whether the coil be 5 high enough to be at the also'to the center of the core or muflle where these are used. The formula for determining this frequency is N 411, where N is the frequency, p the resistivity of the material, ,u. the permeability and 1 is the depth of penetration, approximating onethird of the distance to which the induction extends.

The higher frequencies have the advantage of requiring lesscapacity to correct the power factor, but have the disadvantage of requiring special generators or other. equipment to supply the 'curent. With magnetic materials low frequencies can be used even on relatively small diameters of stock; but when the stock is non-magnetic, unless it be used if too deep penetration of induction into the stock is to be avoided.

y invention is independent of the numberl of turns per coil and of the detail of the C01 an or in parallel, with coils, single, in series or in parallel and with great variety of current supply. I prefer to water cool the coils and where the inductor coil com rises more than one turn, I prefer to use condiictors having one dimension considerably greater than the other in cross-section and with the greater dimension radial to the axis of the coil,

water cooled or not. y invention is applicable to magnetic or non-magnetic materials whether solid or otherwise and to heating of hollow or solid materials directly by the RI heat development in the materials themselves, wholly or in part, by heat conduction from a casing or core or muflle within which RI heat is developed.

In operation the material to be heated maly] be progressed through the coil or throug one about the muflle,'stepeby-step or continuously or, much less desirably, may be inserted therein and withdrawn. Considering the continuous operation, by odds the most advantageous form, the object or material to be heated is fed through at a rate such. that with the energy available and at the frequency determined upon, it will reach the required temperature or a temperature just proper temperature at the point of use as it emerges from the final coil or. turn. Heatin terial to the point at which it gins to lose its magnetism maybe effective at a relatively low frequency though, with small stock, or

ause of expense of power factor correction, very desirably at a frequency higher than available from line sources of supply and heating beyond the decalescence point will be performed at a much higher frequency.

large in diameter, high frequencies must be and radiation transformer second magnetic masupply.

In view of my disclosure herein other forms and-uses of my invention will undoubted]; occur to those skilled in the art differing rom mine in adaptation to special uses, suiting the preference or whim of the individual designer or for the purpose merely of avoiding copying of my forms and it is my purpose to include herein all such'as come within the reasonable spirit and scope of whatI regard as a very broad invention.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is 1. In the art of electric heatin ,'a source of alternating current supply, a p urality of helical coils having their axes in line, connections from the source of supply separatey to .each coil, capacitative means within said connections and a plurality'of discharge gaps, one across-the coils for supplying high frequency oscillations to the coils from said current suppl 2. In the art of inductive electric heating, a commercial source of alternatin current, an inductor coil connected therewith, a circuit including the source and coil power factor corrective means to offset the inductan e of the coil, a transformer primary fed by said source, a transformer secondary in inductive relation to the primary, a second inductor coil-axially in line with the first and fed from said transformer secondary, capacity in the circuit said secondary and-second coil, a discharge gap across the circuit of said secondary, convertin the frequency of the current supplied by sai secondary to a higher frequency and means for passing an electrically conductive article to be heated through said coil to receive successive increments of heat by induction from the current therein.

3; In the art of a pair of inductor coils, a source of alternating current of commercial uency, connections for one of said coils across the source of supply m said source, condenser power factor corrective means for said coil, a transformer primary connected ary in inductive relation to the primary, wholly se arate connections from the. secondary for inductive electric heating,

with said source, a

e second coil, in-

connected with the circuit i between eluding a discharge gap and condensers, and.

means for passing article to be' heated through said coilv to receive succesive duction from the current therein 4. In the m of electric induction heatin a source of alternating current of commercial frequency, an inductor coil across the an electrically conductive crements .of heat by insource of supply of said source, power factor corrective means for said inductor coil,

I a second inductor coil, connections for the second coil, also across the line of said source and including capacity and a discharge gap across which the voltage-of the source is Suficient to cause discharge and means for passing an electrically conductive article to be heated through said coil to receive succesive increments of heat by induction from the current therein.

5'. In the art of inductive electric heating, a hollow helical coil, a source of electric current therefor, means including a discharge gap and a condenser for supplying high fre- 'quency therefrom to the coil and supporting a means for moving an article to be heated having larger length than width or thickness through the coil while it is being-subjected to the heating" efiect or the coil;

6. In the artof inductive electric heating,

a hollow helical coil, a source of electric current therefor, transformer means for applying current of the frequency of the source to said coil, meansincluding a discharge gap and a condenser'for applying a higher frequency from the source to said coil and supporting means for an article to be heated and moved lengthwise through said coil.

7 In the art of inductive electric heating,

a plurality of coils axially aligned, a source 7 of alternating current therefor, means including a discharge gap and a condenser for increasing the frequency of current fed from the source of current through said coils, and

means'for supporting an articleto be heated so that it can be moved through the coils and receive the cumulative efiect of the current induced gay said coils.

40 DWIN ITGHNORTHRUP. 

